Cryogenic air compressor with air dehumidifying means



Feb. 10 1970 F. M.-B-IRD 3,494,138

CRYOGENIC AIR COMPRESSOR WITH AIR DEHUMIDIFYING MEANS Filed Jan. 2, 1968 INVENTOR.

Forrest M. Bird B15244, #444 m Attorneys United States Patent O.

US. Cl. 62151 7 Claims ABSTRACT OF THE DISCLOSURE Cryogenic air compressor having means for dehumidifying moist air before compression and for silencing the compression so that it can be utilized as a portable automatic source of dry compressed air with acceptable noise levels for clinical and industrial applications.

BACKGROUND OF THE INVENTION With conventional air compressors, upon compression of air, dynamic components of the compressor must be cooled to prevent excessive heat rise in compression areas. When the gases are partially decompressed and cooled, suspended water vapor condenses and accumulates as a liquid in the system. The amount of water accumulation is proportional to the relative humidity and temperature of the entrained ambient air, the volume of air compressed and the compressional temperature rise and the decompressional temperature fall. There is an additional problem in that compressors utilized for such purposes are often relatively noisy and must be located remote from the operational area. In geographical areas where ambient temperatures and relative humidities are high, air is often compressed outside under hot, humid conditions and then transported into air conditioned buildings. This steep temperature gradient from the outside air source to the inside point of utilization causes condensation of water in the plumbing system used for the compressed air. Condensation increases in proportion to rise in ambient temperature and relative humidity. Under certain conditions, condensation may occur which is in excess of the capacity of any condenser provided in the system leading to water delivery into pneumatic powered instruments. compressed air used to power medical respirators and other precision instrumentation must be clean and dry. In addition, there is a requirement that the source for the compressed air be relatively quiet. There is, therefore, a need for a new and improved apparatus for producing clean and dry compressed air.

SUMMARY OF THE INVENTION AND OBJECTS The cryogenic air compressor comprises housing means which forms first and second compartments. A refrigeration unit is provided for refrigerating the first compartment. An air compressor is mounted in the second compartment. The housing means for the second compartment provides means for reducing the sound from the air compressor to an acceptable noise level. Means is provided for supplying air to the air compressor so that it first must pass through the first compartment and is cooled therein to precipitate substantially all the moisture therein before it can pass into the air compressor in the second compartment. After the air has been compressed in the second compartment, means is provided for delivering the air to suitable outlets where it can be used.

In general, it is an object of the present invention to provide a cryogenic air compressor which can be utilized for delivering clean and dry compressed air at a noise level acceptable for clinical and industrial applications.

Another object of the invention is to provide a cryogenic air compressor of the above character which can be Patented Feb. 10, 1970 ICC manufactured with the use of a conventional refrigerator.

Another object of the invention is to provide a cryogenic air compressor of the above character in which the air compressor is mounted within the refrigerator and the entrained air for the air compressor passes through the freezer compartment of the refrigerator.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment is set forth in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a perspective view of a cryogenic air compressor incorporating the present invention.

FIGURE 2 is a cross-sectional view of the cryogenic air compressor shown in FIGURE 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The cryogenic air compressor shown in the drawings consists of housing means which forms a first compartment 12 and a second compartment 13. The housing means 11, the first compartment 12 and the second compartment 13 in the present embodiment of the invention are formed by a conventional refrigerator such as a standard 12 cu. ft. frost-free commercial refrigerator which is provided with a top freezer compartment which serves as the first compartment 12, and a lower refrigerated compartment which serves as the second compartment 13. Thus, in such a refrigerator, the housing means takes the form of a cabinet 16 which has a box-like configuration and which forms two rectangular compartments 12 and 13 which are insulated from each other and from the outside air by insulation 17.

Such a conventional refrigerator also includes a top hinged door 18 for closing the freezer compartment 12 and a lower hinged door 19 for closing the refrigerated compartment 13. Such a conventional refrigerator is also provided with a lower compartment 21 which has mounted therein a standard refrigerator compressor 22 which is unaltered. A decorative removable panel 23 is provided for covering the lower compartment 21. The cabinet 16 is mounted on four castered wheels 24 so that the entire cryogenic air compressor can be readily moved from one location to another. The refrigerator compressor supplies a cooling fluid in the conventional manner to evaporator coils 26 mounted in the first compartment 12 for cooling the compartment 12 to a temperature below the freezing temperature of water and automatic means is provided for maintaining this compartment at this lower temperature. In addition, conventional means is provided for periodically defrosting the evaporator coils 26 every 12 hours. Defrost water collects in a tray beneath the evaporator coils and drains through a tube to the evaporator tray at the bottom of the refrigerator where it evaporates to the atmosphere. This portion of the apparatus is conventional and has not been illustrated in the drawings. The cooling openings for normally cooling the refrigerator compartment 13 have been blocked so that the compartment 13 is separated from the evaporator coils 26.

An oil-free compressor system 31 is mounted within the second compartment 13. Such a system is substantially conventional and includes a large tank 32 which is mounted upon a pair of saddles 33 mounted on the bottom wall of the cabinet which forms the compartment 13. An air compressor 34 which is driven by an electric motor 36 is mounted upon a saddle assembly 37 mounted on top of and at one end of the tank 32. A pair of input tubes 41 and 42 are provided. As can be seen particularly from FIGURE 2, the upper ends of the input tubes are disposed within the first compartment 12 and are substantially semi-circular in shape so that the inlet ends of the tubes are disposed substantially equi-distant from the top and bottom sides of the compartment and are spaced inwardly from each side of the compartment. The inlet tubes '41 and 42 extend downwardly from the compartment 12 and enter the compartment 13 where they are connected to the compressor 34. The output of the compressor 34 is suppliedthrough piping 43 to the tank 32. A pressure control switch 44 is connected into the piping 43 and is connected into a terminal box 46 mounted in the compartment 21. The terminal box 46 is connected to a suitable source of supply through the plug 47 such as 110 volts, 60 cycle A-C.

The control switch 44 is connected by circuitry 48 to the motor 36 so that the motor 36 operates the air compressor Whenever the pressure within the tank drops below a predetermined pressure and stops the motor when the pressure within the tank 32 is above the predetermined pressure as, for example, below 65 p.s.i. and above 80 p.s.i. A digital hour meter 49 is connected to the control switch and is utilized for determining the number of operating hours of the compressor 34.

Means is provided for supplying air from the tank 32 so that it is accessible from outside of the cabinet 16 and consists of piping 51 connected into the tank 32. A tank pressure gauge 52 is connected into the piping 51. A manual pressure release device 53 is also connected into the piping. Similarly, a water filter 54 of conventional type is mounted in the piping to remove any residual water within the air. An adjustable pressure regulator 56 is mounted in the piping as is a manually operated valve 57. The piping 51 extends through the side wall of the cabinet and is connected to a manifold 58 which is provided with a plurality of outlet nipples 59. The flow through any one of the nipples is controllable by means of a needle valve provided in the manifold assembly for each of the nipples. In addition, a manually operated valve 62 is provided outside of the cabinet.

Means is provided for cooling the compartment 13 whenever the temperature within the compartment rises above a predetermined temperature as, for example, above 80 F. Such means consists of a fan 66 mounted on the rear wall forming the compartment 13 and which is driven by a motor 67. The motor 67 is controlled from a thermostat 68 that has a sensing element 69 disposed near the top of the compartment 13. The fan 66 is provided for discharging air from the compartment 13. A bafiied opening (not shown) is provided in the side wall of the cabinet forming the compartment 13 to permit cooling air to enter into the compartment 13.

Means is provided for supplying atmospheric air from the outside to the first compartment 12 and consists of openings 76 provided in the wall of the cabinet forming the compartment 12 so that air can pass through an inlet filter 77. The air passes through the inlet filter into the compartment 12 where it is cooled to F. or below.

Operation and use of the cryogenic air compressor may now be briefly described as follows. Let it be assumed that the cryogenic air compressor has been connected to a suitable source of electric power and that the air compressor is under the control of the control switch 44 to maintain a relatively constant supply of compresed air within the tank 32. Also, let it be assumed that the pressure drops below 65 p.s.i. Within the tank and that the compressor starts operating. As this occurs, cool air within the freezer compartment 12 which is preferably below 10 F. is drawn into the air compressor and compressed and supplied to the tank 32. As the air is withdrawn from the compartment 12, additional air is drawn from the outside air through the inlet filter 77 and is immediately cooled in the compartment 12 which, as pointed out above, is preferably below 10 F. As the air is cooled, any water within the air is precipitated out of the air so that by the time the air is drawn into the inlet tubes 41 and 42, it is cold and dry; The air compressor 34 serves to compress suflicient air until the pressure Within the tank is raised to the desired maximum pressure as, for example, 80 p.s.i., at which time the air compressor shuts off.

-It has been found that the capacity of the freezer compartment is such thatit can readily provide cold, dry air for use by the air compressor. Since the refrigerator cabinet 12 is wellinsulated, it also serves as an excellent insulator for sound and,'therefore, it is possible for the air compressor to operate within the compartment 13 with a very acceptable noise level. In view of this fact, it is possible to provide the cryogenic air compressor at locations where it is desired to utilize the air, eliminating the necessity for removing the air compressor and long lines of piping.

Thus, it is possible to provide clean, dry air at the location at which-it is desired to be used at a very acceptable noise level. Large foreign particles are filtered out of the entrained air by the inlet filter 77. Entrained pathogenic organisms are exposed to sub-ambient temperatures in the -20 C. range before being exposed to the high temperatures created by the compression heating in the air compressor 34. Any residual moisture within the air is removed by the filter trap 54 which contains a self-purging filter element.

It has been found that it is relatively inexpensive to construct the cryogenic air compressor in view of the fact that it is possible to utilize a conventional refrigerator with minor modifications. The automatic self-defrosting feature of the conventional refrigerator provides a simple means for purging water from clinical air which is much more dependable than standard water traps heretofore provided. Under conditions of high ambient air humidity, the apparatus is still able to function very efiiciently and remove 99% of the water from entrained air It has been found that a single cryogenic air compressor of this type mounted in a refrigerator can provide sufiicient compressed air to operate the average out-patient pulmonary therapy clinic with up to ten stations, or two or 'more high flow intensive care ventilators used simultaneously with moderate reserves.

I claim: p

1. In a cryogenic air compressor, housing means forming first and second closed compartments, a refrigerator unit for refrigerating said first compartment, an air com pressor mounted in said second compartment,.said housing having insulation to insulate said first and second compartments from the outside ambient air whereby there cluding piping connecting said first compartment-to said air compressor, and means 'for withdrawing 'air from the air compressor after it is compressed.

2. An air compressor as in claimml together, with means for cooling the second compartment .when the temperature within the second. compartment goesabove apredetermined temperature. I

3. An air compressor as inclaim 1 together with means for periodically defrostingjsaid firstcompartment,

4. An air compressor as in claim 1 together with means for filtering the air before'fit passes into the first compartment. H V

5. An air compressor as in clair'n'l wherein said housing means is formed as a single cabinet.

6. An air compressor as in claim 1 together with a storage tank mounted insaid second compartment connected to said air compressor and automatically operated means measuring the pressure in said ta'nk'for starting said air compressor whenthe pressure in said-tank drops below a predeterminedpressure and for stopping said air compressor when the pressure in said tank goes above a predetermined pressure.

7. In a cryogenic air compressor, housing means forming first and second compartments, a refrigerator unit for refrigerating said first compartment, an air compressor mounted in said second compartment, said housing having insulation to insulate said first and second compartments from the outside ambient air whereby there is a minimum of heat transfer from the outside to the inside of the first compartment and a minimum of noise transfer from the second compartment to the outside air, means for supplying air to the air compressor so that it first passes through said first compartment to precipitate moisture from the air, means for withdrawing air from the air compressor after it is compressed, a storage tank mounted in said second compartment connected to said air compressor, automatically operated means measuring the pressure in said tank for starting said air com- References Cited UNITED STATES PATENTS 2,187,470 1/1940 Collins 62-283 2,477,772 8/1949 Simpson 6293 2,867,988 1/1959 Brandt 62-93 MEYER PERLIN, Primary Examiner US, Cl. X,R, 6293, 283 

